Ethylene and propylene, light olefin hydrocarbons with two or three atoms per molecule, respectively, are important chemicals for use in the production of other useful materials, such as polyethylene and polypropylene. Polyethylene and polypropylene are two of the most common plastics found in use today and have a wide variety of uses for both as a material fabrication and as a material for packaging. Other uses for ethylene and propylene include the production of vinyl chloride, ethylene oxide, ethylbenzene and alcohol. Steam cracking or pyrolysis of hydrocarbons produces essentially all of the ethylene and propylene. While hydrocarbons used as feedstock for light olefin production include natural gas, petroleum liquids, and carbonaceous materials including coal, recycled plastics or any organic material, an important source is naphtha where larger paraffins and naphthenes are cracked to produce olefins.
One means of producing ethylene and propylene is an olefin cracking process, where larger olefins in the C4 to C8 range are cracked to produce propylene and ethylene in high propylene to ethylene ratios. Typically, an olefin cracking process is integrated with a naphtha cracking unit, and the propylene is dramatically increased. The use of an olefin cracking unit can take lower value C4 to C6 byproducts to produce additional propylene and ethylene.
The olefin cracking process uses a catalyst that deactivates during regeneration. This leads to replacement of the catalyst when regeneration no longer sufficiently reactivates the catalyst.